Rename chart files.
Add a views folder under public/assets/css, put all view-specific CSS files under it.
Make chartNetworkForce interface more fluent like other charts.

Also stop loading coappear data with d3.js in chartCoappear, and instead load it in the AngularJS controller the same way as any other data. Should speed up data loading in ChapterController because it's now loading both JSON files concurrently instead of serially.
Change default data so the nodes and links properties are defined.
Make chartCoappear interface more fluent like other charts.
Add neighbors to each node on server side rather than client.